Inhibitor



Patented Aug. 19, 1930 UNITED STATES amine PATENT OFFICE IRA. WILLIAMS, 01 LAKEWOOD, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE GEASSELLI CHEMICAL COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF DELA- WARE INHIBITOR Il'o Drawing.

The present invention relates to inhibitors, their use to control the action of acids upon metals, and to processes of cleaning, pickling, scaling, or removing oxides and other acid soluble deposits from metallic articles.

It is Well known that the addition of certain, mostly organic compounds to acids diminishes or even entirely suppresses the actions of acids upon base metals. Considerable use is made of this property of such compounds, commonly called inhibitors, in the protection of metallic articles or in cleanv ging, pickling, or other treatments preparatory to working of iron and steel arti- 1 cles. Formaldehyde, benzaldehydgfu rfural, and ac'e'taldehyde haveyafnongst others, been suggested-for the purpose of inhibiting the action of acids upon iron and steel. Actual large scale tests of these inhibitors have demonstrated that their use is impractical. They develop unpleasanLQflOrs during pickling operations m'seare most obnoxious to the workmen. So far as I am aware, no extended application of these aldehydes for this particular purpose has ever been made.

I have now found that certain other organic chemicals have, in a remarkable degree, the property of inhibiting the action of acids upon metals without in any other manner exhibiting objectionable or detrimental efiects.

My novel inhibitors are acrolein..-derivatives. in which the al haandlhetacarbon atoms are substituted y hydrocarbon'i'adicles. They can be represented by the general formula RCCHO ll 40 CH-R in which R and R are hydrocarbon radicles.

These substituted acroleins are easily prepared from aliphatic aldehydes, as, for instance, by the actions of dilute aqueous Application filed August 9, 1928. Serial No. 298,635.

caustic alkali thereon. Alpha-methyl-betaethyl acrolein is, for instance, prepared from n propyl-aldchyde; n butyraldehyde produces alpharethyl;betapropylaiiQlein. These and" similarly subtsituted acroleins, such as alpharopylsbetwhutyl-acrolein, all show tli"i"rih'biting efi'ect. Butyraldehyde being commercially available at the present time, the alpha-ethylsbeta-propyl-acrolein derived therefrom is the most convenient product applicable to my invention. It shows in a remarkable degree the favorable inhibiting properties of this group of chemical compounds. These substituted acroleins are characterized by high boiling point and rather pleasant odor. They distinguish themselves favorably in this respect from acrolein itself which has an unbearable, pungent, and irritating odor.

Very small amounts of my novel inhibitors need only be added to the acid to prevent or materially decrease the evolution of hydrogen and dissolving of metal in such acids.

Zin iron, tin, etc., added to dilute hyc rochloric acid containing less than one percent of ethyl-propyl-acrolein will remain practically inertand even on heating no material evolution of hydrogen will be noticed. Even dilute nitric acid containing my novel inhibitors will hardly attack such base metals. The action of nitric acid in concentration at which it reacts as an oxidizing agent is, however, not inhibited by'my substituted acroleins.

The main application of my novel inhibitors is in pickling operations and cleaning of metal articles. such as pipe lines for removing rust incrustations or for freeing boiler tubes from scale. It is in such operations essential that the rust or scale be dissolved easily and the metal be as little attacked as possible. Dilute mineral acids are commonly used for the above urposes; while the scale and other incrustations are easily removed, an attack of the bare metal is unavoidable with resulting weakening of the material and unnecessarily high consumption of acid. There are quite a number of other objectionable features to the pickling and cleaning of iron and steel with ordinary acids, which are well known to those skilled in the art. Most of these are overcome by the use of a pickling bath or cleaning solution which readily attacks and dissolves the coating and leaves the metal unaffected. The use of the substituted acroleins as set forth herein allows now the preparation of such pickling baths and cleaning solutions. About two parts. or less. by weight of alphaethyl-beta-propyl-acrolein added to one thousand parts of 6% sulfuric acid provides a convenient pickling bath to be used at about 150 F. Certaiut'olloidal naterials are sometimes added t?) pickling baths'for the purpose of producing a foam and in this manner reduce the dissemination of finely divided acid 'particles throughout the pickling room, saponin,

molasses, sulfite cellulose waste being amongst those in common use. My novel inhibitors can likewise be added to such compounded dilute acid solutions and the same inhibiting action obtained. Pickling baths or cleaning solutions containing other than sulfuric acid, e. g.. hydrochloric acid or sodium bisulfate, can likewise be improved by the addition thereto of small amounts of my alpha-betasubstituted acrolein.

My novel inhibitors are only slightly soluble in ordinary pickling baths. and for this reason it is preferred to add same only at the time of use. A convenient form for supplying my inhibitors to the pickling room consists in a mixture or emulsion of the acrolein with sulfite cellulose waste diluted with or dissolved in water. Forty-five parts by weight of sulfite cellulose waste, 10 parts of ethyl-propyl-acrolein and 45 parts of water form a free flowing dark emulsion of not unpleasant odor. One pound of this added to about 1500 parts of 6% sulfuric acid produces an excellent pickling bath. It is sometimes desirable to furnish a solid inhibitor; this can easily be achieved bv absorbing the liquid acrolein upon nitre cake with further addition of solid sulfite cellulose waste if deemed advisable. A compound of this type is. for instance. obtained by mixing 30 parts by weight of sulfite cellulose waste with parts powdered or granular nitre cake and 10 parts ethyl-propyl-acrolein. About of 1% of this compound added to a pickling bath of the usual acid concentration will materially improve it by reducing the dissolution of the metal and diminishing the evolution of hydrogen, and consequently the obnoxious mist evolved from an ordinary pickling bath.

The following table shows the results of laboratory tests made on the inhibiting action of varying amounts of my novel inhibitor when added to a diluted sulfuric acid.

The tests consist in measuring the gas evolved after given intervals of time when a piece of steel is allowed to remain in contact with an aqueous solution of sulfuric acid. The test pieces consisted of ordinary black mild sheet steel of 28 gauge, each 2" square, so that the total surface was 8 sq. in. The solution was 34% sulfuric acid and the tests made at room temperature:

cc gas evolved after Compositjton ofinhibmy" of bath 1 hour 2 hours 6 hours 20b0urs 55 210 1010 2000 Sodium bisulfate 66%73. Sulfite cellulose waste 0 1 22 58 175 350 0 1 None None 4 17 Do 0.5 None None 1 2 gatlium bifiupate 63% te ce uose was e 32% and 0.5 None 1 5 16 propyl acrolein 5%---.

The following are the results obtained in a. I

position of the inhibitor was 45% sulfite cellulose waste, 45% water, and 10% alphaethyl-beta-propyl-acrolein. The amount of the acrolein derivative contained in the original bath corresponds therefore to about 0.00

A total of 143.28 tons of steel nut and wire stock was pickled in this test. A total of 51 lbs. of the above compounded inhibitor and 5,200 lbs. 66 B. sulfuric acid were used. This amount of acid is approximately 10% below that normally used when no inhibitor is added to the bath. Aside from the above saving of acid and corresponding saving in metal, the pickling produced a cleaner and less damaged stock, showing less pitting than when sulfuric acid alone is used.

The amount of my novel inhibitors to be added to dilute acids used for the cleaning or pickling of metallic articles is not very critical and can vary within wide limits. Less than of 1% of the acrolein compound figured on the weight of the dilute acid will usually produce the maximum effect. The type of acid used and its concentration do not seem to affect greatly the beneficial action of my inhibitors.

Mixtures of my various inhibitors or mixtures of these with other known inhibitors can be used and similar improved results obtained.

It will be understood that my invention is 252. COMPOSITIONS,

not limited to the particular substances and procedures mentioned herein, but that it comprises the application of my novel inhibitors to the various operations carried out under various conditions involving the action of acids upon metal articles where it is desired to free the metal from acid soluble incrustations with least possible attack of the metal itself.

I claim:

1. As a compounded inhibitor for use in cleaning and pickling metals, a mixture of a foam-producing agent and an acrolein compound in which each alpha and beta carbon atom is substitued by a hydrocarbon radicle.

2. As a compounded inhibitor for use in cleaning and pickling metals, a mixture comprising sulfite cellulose waste and alphaethyl-beta-propyl-acrolein.

3. A solid inhibitor for use in cleaning and pickling metals, alpha-ethyl-beta-propylacrolein absorbed upon a mixture of nitre cake and sulfite cellulose waste.

4. A pickling and cleaning bath for metals comprising a dilute acid having a small amount of an alpha-beta-substituted acrolein incorporated therein.

5. A pickling and cleaning bath for metals comprising a dilute mineral acid containin a small amount of an acrolein derivative 0 the general formula B-C-CHO in which R and R are hydrocarbon radicles.

6. A pickling and cleaning bath for metals comprising a dilute mineral acid containing a small amount of alpha-ethyl-beta-propylacrolein.

7. A pickling and cleaning bath for metals comprising dilute sulfuric acid containing a small amount of alpha-ethyl-beta-propylacrolein.

8. Process of pickling and cleaning metal articles which comprises treating the articles with a liquid consisting essentially of dilute mineral acid and containing a relatively small but effective amount of an acrolein derivative .propyl-acrolein.

In testimony whereof I aflix m signature.

in wrdnnuus. 

